Historically, aircraft wing lift and drag flight characteristics are altered using trailing edge flaps (ailerons) and elevators. Shape-changing of a wing is a technique of achieving the goals of trailing edge flaps (ailerons) and elevators to steer the aircraft, and alter the lift-to-drag (efficiency) profile of the aircraft. Wing shape-changing has the added benefit of being more efficient than flaps due to the lower induced drag produced by sharp edges created by flaps.
Current methods of wing shape-changing that have been proposed include the use of motors and even pneumatic or fluid-based artificial muscles as actuators to change the shape of the wing in-flight. Due to the weight of traditional motors and air or fluid compressors used to activate fluid driven artificial muscles, as well as the associated mechanical moving parts to support the heavy motors or actuators, current designs limit wing shape change to simple curvature of the trailing edge of the wing or sub-optimally efficient segmentation of the wing into static and articulating sections. In other current designs, wing shape change is limited to simplistic changes to the cross-sectional shape of the airfoil or change to only a limited portion of the airfoil to minimize the use of heavy motors, air or fluid compressors and traditional motorized actuators.
Creation of a wing shape-changing design that incorporates a high strength-to-weight ratio installed-in-wing actuation method is desirable for individual wing-rib actuation flexibility and associated variability of wing shape change across the entire wing span. The present invention uses high strength-to-weight ratio polymer artificial muscles as actuators of a wing rib apparatus. The polymer artificial muscles and their associated creation are described in International Patent # WO2014/022667A2 to N. LI, et al, 2014. Use of these polymer artificial muscles as actuators within a wing rib allows for independent wing rib articulation and highly variable and controllable in-flight wing shape change for optimal efficiency and to steer the aircraft without the use of trailing edge flaps (ailerons) and elevators.